Folding rotor blade



April 24, 1951 M. D. BUlVlD FOLDING ROTOR BLADE Filed July 18, 1947 2Sheets-Sheet 1 MICHEL D. BUIVID INVENTOR ATTORNEY April 24, 1951 BU|V|D2,549,886

FOLDING ROTOR BLADE Filed July 18, 1947 2 Sheets-Sheet 2 gr R a (D O G(D I @321 T MIGHEL'D. BUIVID INVENTOR I MK ATTORNEY Patented Apr. 24,1951 UNITED STATES PATENT OFFICE FOLDING ROTOR BLADE Michel D. Buivid,Milford, Conn assignor to United Aircraft Corporation, East Hartford,Conn., a corporation of Delaware Application July 18, 1947, Serial No.761,975

Claims. 1

This invention relates to an improved mechanism for folding rotor bladesof rotary wing aircraft without injury to the control mechanism.

Accordingly, an object of this invention is to provide a rotorblademounting assembly which will permit the blade to be folded and thecontrols to be automatically disengaged by a simple rapid process.

Another object of this invention is to provide a hub assembly for rotarywing aircraft which automatically disengages the pitch control systemwhen the blade is released for folding.

A further object is to provide means for folding rotor blades into amore compact space.

A further object is to provide automatic mechanism to disengage thepitch controls when the rotor blades are folded.

Another object is to provide mechanism which automatically engages thecontrols only when the blade is properly positioned with respectthereto.

Still another object is to provide a method of folding rotor bladeswhich will simplify ground handling.

The foregoing, and other objects, will be obvious or pointed out in thefollowing specification and claims.

In the drawings:

Fig. 1 is a side elevation of a helicopter with the rotor blades foldedaccording to my invention;

Fig. 2 is a fragmentary perspective View;

Fig. 3 is a plan view showing the blade in the assembled or flightposition; and

Fig. 4 is a view of Fig. 3 taken along line 4-4 with parts broken awaywith the blade lowered.

In my United States Patent No. 2,405,777, I have shown a method offolding the rotor blades to rest upon a jack on the tail cone of thewellknown helicopter configuration of a single main rotor and a torquecounteracting tail rotor. The method disclosed in my patent involves twosteps; releasing the rotor blade for folding and disconnecting the pitchcontrol mechanism. When the blades are returned to the operativeposition the pitch control and the blade must be secured. It is thepurpose of the present invention to improve upon the mechanism shown inmy patent to provide a simple mounting device whereby releasing theblade for folding movement automatically disconnects the pitch controlmechanism. When the blades are returned to the flight position, thepitch control mechanism is automatically engaged. This results in amaterial time saving which is of particular advantage aboard navalvessels where the flight deck must be cleared for further operations asrapidly as possible.

Fig. 1 shows a helicopter N3 of conventional configuration having asingle main rotor [-2 and a torque counteracting 'tail rotor l4. Therotor has three blades I6, [8, 20 which are shown in the position theyoccupy when folded according to my invention. When blade 20 overlies thetail cone the upper taper pin, to be described hereinafter, is releasedto allow the blade to rest on jack 22. The port'and starboard blades I6,I8 are supported by slings 24 with the chord of the blade generallyvertical. This provides a stable support and allows the blades to lieagainst the tail cone, reducing the probability of damage thereto.

Referring to Figs. 2 through 4, the port blade I6 is mounted in fitting26 which has an integral mounting cuff 28 with upper and lower sets ofears 30 parallel to the chordline of the blade. Ears 30 are adapted tomesh with ears 32 on the cuff of the sleeve 34 and have holes 36 whichalign with holes 38 in cars 32. Taper pins 48, 42 pass through thecooperating holes 36, 38 to hold the blade in its flight position. Pins40, 42 are driven into a tight fit by means of a rawhide mallet and nuts44, 46 are then used to further draw up on the taper. When the uppertaper pin is removed, the blade may be pivoted about the lower pin 42which acts as a hinge, as shown in Fig. 2. Since the pins aresubstantially parallel to the chord of the blade, the tip'of the blademay be swung down to ground level when the upper pin 4!! is released. Aswill appear hereinafter, this feature permits of safe, easy groundhandling of the blade.

Sleeve 34 is mounted on internal bearings 33,35 which resist axialmovement but permit rotation about the sleeve axle 43 to change thepitch of the blade when the blade is assembled for flight. Therotational movement and position of the sleeve is controlled by thepitch control mechanismithrough push pull rod 5?! which is actuated bythe usual rotating and stationary star assembly, not shown, and isconnected, by means of pin 52, to the bifurcated'end of the collar arm54. Collar arm 54 is integral with collar 58 which is mounted on bearingring nut 37 in aconventional manner. On the upper portion of collar 56is lug 58 which has tapered hole 61] passing therethrough. A springloaded device 66 is mounted Within aligned holes in ears 62, 64 on topof sleeve 34 and connects collar ear 58 to sleeve 34 to transmit pitchcontrol movements to the blade of the sleeve 34 with respect to collar56 without loading the pitch mechanism.

The spring loaded device 66 comprises the central tube 14 which has alatch pin 68 slidably mounted in the left-hand end thereof (Fig. 4) andrestrained from movement completely out of the tube by means of aninternal shoulder I6 on tube 14 and cooperating shoulder 18 on pin 68. Alatch pin 88 has a cylindrical end fixed in the right-hand end of tube74 by, a pin 8! and projects beyond tube 14 and is slidably received inthe hole in ear 64. The free end of pin 88 is suitably tapered tofacilitate entry thereof .into the like tapered hOle 68 in lug 58.Inside the tube and between the facing ends of latch pins 68 and 88 is apreloaded safety spring 82, the purpose of which will be more fullydescribed hereinafter. Compression spring 18, outside tube 14, bearsagainst ear 64 and guide plate 12 which seats against an externalannular shoulder 83 on tube 14.

As shown in Fig. 3, when the rotor is assembled the middle ear 38 oncuff 28 bears against the end of latch pin 68 and displaces it to theright. This force acting through spring 82 moves pin 88 and tube 14 tothe right against the bias of spring 18 which constantly urges thedevice 66 into the position shown in Fig. 4. The safety spring 82 drivesthe latch pin 88 into operative engagement with the holes 68 in ear 58on collar 56. As shown in Figs. 2 and 4, when the upper taper pin 48 isremoved and the blade is pivoted about the lower hinge pin 42, thedisengaging spring 18 moves the latch pin 88 out of engagement with thecollar arm ear 58. The blade and the sleeve are now freely rotatableabout the sleeve axis and, therefore, the blade may be folded backagainst the tail cone of the helicopter without damaging the pitchmechanism.

When the blade is returned to the flight position, the middle ear 38moves the latch pin 68 inwardly against the force of spring. Should theholes in the ears 64 and 58 be misaligned, the safety spring 82 willcompress when latch pin 88 is unable to move into the hole in the ear58, preventing damage to the mechanism. The taper pin 48 may be driventhrough the holes 36, 38 in the ears 38, 32 and the blade'may then berocked about its pitch changing axis until the holes in ears 64, 58become aligned, at which time the spring 82 drives latch pin 88 intoengagement with collar arm ear 58. As an alternative to rocking theblade about its axis, the pitch control stick may be worked until thecollar arm becomes aligned with the sleeve and latch pin 88 is driveninto engagement with tapered hole 68.

All the blades are mounted in the same manner but it will be obviousthat the blade on the starboard side must be folded in the oppositedirection with respect to the direction of blade rotation.

This construction permits simple, rapid, and safe ground handling of theblades during the folding process. When the taper pin 48 is removed theblade is free to pivot about hinge pin 42, allowing the blade tip todrop to a crewman waiting on the ground. The crewman now walks the bladeback adjacent the tail cone and places it in sling 24. This movementcause the sleeve 34 to rotate on bearings 33, 35 and will also causefurther movement of the blade about h nge pin 42. Since the pitchmechanism is disengaged there is no danger of damage to the controls.Since the blade may be moved freely about the hinge pin 42 and/or thepitch changing axis the crewman can conveniently handle the blade safely, even in winds of high velocity. When the blade has been placed inthe sling it is more secure and less vulnerable. It will be apparentthat this device provides a convenient and simple blade folding processwhich precludes damage to the controls and minimizes the danger ofdamage to the blades.

It is to be understood that the invention is not limited to the specificembodiment herein illustrated and described, but may be used in otherways without departure from its spirit as defined by the followingclaims.

I claim.

1. In a helicopter having a sustaining rotor and a body includin a tail,a blade mounted on said rotor, blade support means cooperating with saidtail, and means for folding said blade to lie adja cent said tail onsaid support means with its chord generally vertical including a hingein the blade root portion having an axis generally parallel with thechord of the blade.

2. In a helicopter having a sustaining rotor and a body including atail, in combination, three blades mounted on said rotor, pitch controlmeans for said blades, means for folding said blade including a hinge inthe blade root portion of each blade having an axis generally parallelwith the chord of the blade, means for automatically releasin said pitchcontrol means upon operation of said folding means, means coacting withsaid tail and one of said blades to support said one blade over saidtail cone, and means cooperating with said tail for supporting theothers of said blades adjacent said tail with the chords of said bladesgenerally vertical.

3. In a helicopter, a rotor hub, a variable pitch blade mounted on saidhub, blade folding means including a hinge in the root portion of saidblade, whereby a combined pivotal movement of said blade about saidhinge and about the pitch varying axis of the blade enables the blade tobe folded and unfolded, means for locking said hinge with said blade inflight position, manually operable means for varying the pitch of saidblade including a member movable with said blade during pitch variationthrough a limited movement which is less than that required about saidpitch varying axis in said blade folding movement, means operativelyconnecting said member and blade in the flight position of the latter,and mechanism operative in response ,to pivotal movement of said bladeabout said hinge for controlling said last mentioned means to connectand disconnect said member and blade.

4. In a helicopter, a rotor hub, a variable pitch blade mounted on saidhub, blade folding means including a hinge in the root portion of saidblade, whereby a combined pivotal movement of said blade about saidhinge and about the pitch.

varying axis of the blade enables the blade to be folded, means forlocking said hinge with said blade in flight position, manually operablemeans for varying the pitch of said blade including a member movablewith said blade during pitch variation through a limited movement whichis less than that required about said pitch varying axis in said bladefolding movement, means operatively connecting said member and blade inthe flight position of the latter, and mechanism operative in responseto folding movement of said amasec blade for operating said connectingmeans to disconnect said member and blade during the latter part of theblade folding movement.

5. In a helicopter, a rotor hub, a variable pitch blade mounted on said"hub, blade: folding means including a hinge in the root portion of said.blade, whereby a. combined pivotal movement of said blade about saidhinge and about the pitch varying axis ofthe blade enables the blade tobe folded and unfolded, means for locking said hinge with saidv blade inunfolded position, manually operable means for varying the pitch of saidblade including a member movable with said blade during pitch variationthrough a limited movement which is less than that required about saidpitch varying axis in said blade folding movement, means operativelyconnecting said member and blade in the unfolded position of the latter,and mechanism operated by said blade during unfolding movement thereoffor operating said connectin means to connect said member and blade.

6. In a helicopter, a rotor hub, a blade mounted on said hub for pitchchanging movement about the longitudinal axis of said blade, means formoving said blade between flight position and a folded positionincluding a hinge in the root portion of said blade having an axistransverse to said pitch changing axis, whereby pivotal movements ofsaid blade about its pitch changing axis and about said hinge axisenable said blades to be moved between said positions, means for lockingsaid hinge with said blade in flight position, manually operable meansfor changing the pitch of said blade including a member movable withsaid blade during pitch change through a limited range which is lessthan the movement required about said pitch changing axis in moving saidblade between said flight and folded positions, means operativelyconnecting said member and blade in the flight position of the latter,and mechanism operative in responsive to folding and unfolding movementsof said blade for disconnecting and connecting said member and blade.

7. In a helicopter, a rotor hub, a blade mounted on said hub for pitchchanging movement about the longitudinal axis of said blade, means formoving said blade between flight position and a folded positionincluding a hinge in the root portion of said blade having an axistransverse to said pitch changing axis, whereby pivotal movements ofsaid blade about its pitch changing axis and about said hinge aXisenable said blade to be moved between said positions, means for lockingsaid hinge with said blade in flight position, manually operable meansfor changing the pitch of said blade including a member movable withsaid blade during pitch change through a limited range which is lessthan the movement required about said pitch changing axis in movingbetween said flight and folded positions, means operatively connectingsaid member and blade in the flight position of the latter, andmechanism operated by said blade as the latter moves about said hingeaxis during folding and unfolding movement for disconnecting andconnecting said member and blade.

8. In a helicopter, a rotor hub, a blade mounted on said hub for pitchchanging movement about the longitudinal axis of said blade, means formoving said blade between a flight position and a folded positionincluding a hinge in the root portion of said blade having an axistransverse to said pitch changing axis, whereby pivotal movements ofsaid blade about its pitch changing axis and about said-hinge, axis.enables said-lblade to be movedbetween the. aforesaidpositions, meansfor locking saidhinge with said blade in, flight position, manuallyoperablepitch changing mechanism including a member movable with saidblade during pitch change through a limited range which is lessthan themovement required about said pitch changing axis in moving said bladebetween said flight and folded positions, means operatively connectingsaid member and blade in the flight position of the latter comprising alatch element constantly biased to release said member, said latchelement having a portion projecting into the path of said blade as thelatter is swung about said hinge axis into flight position for movingsaid latch element against its bias intoposition to connect said memberand blade.

9. In a helicopter, a rotor hub, a stub shaft mounted on said hub, ablade having a root sleeve journalled on said shaft for pitch changingmovement about the longitudinal axis of the blade, means for moving saidblade between a flight position and a folded position including a hingebetween said root sleeve and said blade having an axis transverse tosaid pitch changing axis, whereby pivotal movements of said blade sleeveand pivotal movements of said blade about said hinge axis enable saidblade to be moved between the aforesaid positions, means for lockingsaid hinge with said blade in flight position, manually operable pitchchanging mechanism including a member journalled on said stub shaftadjacent said sleeve and movable with said sleeve during pitch changethrough a limited range which is less than the movement required aboutsaid pitch changing axis in moving said blade between said flight andfolded positions, aligned apertures in said sleeve and member, a plungermounted in said sleeve apertures in position to project into theaperture in said member, and means constantly biasing said plunger outof the aperture in said member, said plunger having a portion projectinginto the path of said blade as the latter is swung about said hinge axiinto flight position, whereby said member and sleeve are operativelyconnected in the flight position of said blade.

10. In a helicopter, a rotor hub, a stub shaft mounted on said hub, ablade having a root sleeve journalled on said shaft for pitch changingmovement of said blade about the longitudinal axis thereof, means formoving said blade between a flight position and a folded positionincluding a hinge between said root sleeve and said blade having an axistransverse to said pitch changing axis, whereby pivotal movements ofsaid sleeve about said pitch changing axis and pivotal movements of saidblade about said hinge axis enable said blade to be moved between theaforesaid positions, means for locking said hinge with said blade inflight position, manually operable pitch changing mechanism including amember journalled on said stub shaft adjacent said sleeve and movablewith said sleeve during pitch change through a limited range which isless than the movement required about said pitch changing axis in movingsaid blade between said flight and folded positions, a plunger mountedon said sleeve in position to project into an aperture in said memberand operably connect said member and sleeve, means constantly biasingsaid plunger out of the aperture in said member, said plunger having aportion projecting into the path of said blade as the latter is swungabout said hinge axis r V 7 into flight position, whereby said memberand sleeve are operatively connected in the flight position of saidblade, said plunger including a tubular member having latch pinsprojecting from the inboard and outboard ends thereof, one of said pinsbeing fixed to said tubula member and the other telescoping therewith,cooperating abutment means on said telescoping pin and tubular memberfor limiting the telescopin movement therebetween, and a compressionspring biasing said telescoping pin in a direction to engage saidabutments and project the outboard pin into the path of movement of saidblade as the latter i moved about said hinge axis into flight position.I

MICHEL D. BUIVID.

1 V I REFERENCES CITED The following references are of record in the Vfile of this patent:

UNITED STATES PATENTS Number Name Date 1,994,465 Cierva Mar. 19, 19352,110,443 Larsen et al Mar. 8, 1938 2,220,109 Larsen Nov. 5, 19402,402,468 Thompson June 18, 1946 2,405,777 Buivid Aug. 13, 1946,

FOREIGN PATENTS Number Country Date 490,151 Great Britain Aug. 10, 1938325,172 Italy Mar. 2, 1935;

